Method for manufacturing a preform, a preform, and a composite article

ABSTRACT

A method for manufacturing a preform includes heating one or more layers of fibrous material containing a plurality of discontinuous structural fibers and a predetermined percentage of thermoplastic material to a first temperature above a softening temperature of the thermoplastic material, forming the one or more layers of fibrous material containing the thermoplastic material into a predetermined shape including at least one raised or depressed region, and cooling the one or more layers of fibrous material having the predetermined shape to a second temperature below the softening temperature to harden the thermoplastic material. The predetermined shape of the one or more layers of fibrous material is retained by the hardened thermoplastic material, and the cooled one or more layers of fibrous material containing the thermoplastic material are permeable.

FIELD

This application generally relates to composites and, more particularly,to preforms, methods of manufacturing preforms, and composite articlesformed therefrom.

BACKGROUND

High-performance composite materials built of layers of structuralfibers have an advantageous combination of high strength and lightweight. Such composite materials may be produced from prepregs or frompreforms. In the prepreg approach, layers of fabrics impregnated with amatrix material such as a resin may be laid up into the shape of acomposite part to be produced. Thereafter, the prepreg is heated to curethe matrix material and provide the finished composite part.

In the preform approach, layers of structural fibers may be laid upsimilarly to the way they are laid up in the prepreg method. Layers ofstructural fibers may be laid up dry, i.e., without the matrix material,and then infused with matrix material, or layers of structural fibersmay be used with a film molding, in which a matrix material is presentbut not liquid at a start of a process but when heated melts to liquidand flows to infuse. The layers of structural fibers may be laid up on atool, then infused with the matrix material, then followed by curing ofthe matrix material. When the layers are laid up on a tool having athree-dimensional geometry, positioning of the layers of structuralfibers may challenging and labor-intensive due to difficulties in layingup each layer such that the structural fibers are oriented at a desiredangle along the geometry of the tool. Additionally, the structuralfibers must be maintained at the desired orientation during infusion andwhile heat and pressure are applied which may add to the complexity offorming the composite article. Furthermore, wrinkling may occur when thelayers of structural fibers are formed into a complex geometry.

Accordingly, those skilled in the art continue with research anddevelopment efforts in the field of composites.

SUMMARY

In one embodiment, the disclosed method for manufacturing a preformincludes heating one or more layers of fibrous material containing aplurality of discontinuous structural fibers and a predeterminedpercentage of thermoplastic material to a first temperature above asoftening temperature of the thermoplastic material. The method furtherincludes forming the one or more layers of fibrous material containingthe thermoplastic material into a predetermined shape including at leastone raised or depressed region. The method further includes cooling theone or more layers of fibrous material having the predetermined shape toa second temperature below the softening temperature to harden thethermoplastic material. The predetermined shape of the one or morelayers of fibrous material is retained by the hardened thermoplasticmaterial, and the cooled one or more layers of fibrous materialcontaining the thermoplastic material are permeable.

In another embodiment, the disclosed preform includes one or more layersof fibrous material. The one or more layers of fibrous material arepermeable and have a shape that includes at least one raised ordepressed region. The one or more layers of fibrous material include aplurality of discontinuous structural fibers and a thermoplasticmaterial retaining the shape of the one or more layers of fibrousmaterial.

In yet another embodiment, the disclosed composite article includes oneor more layers of fibrous material. The one or more layers of fibrousmaterial have a shape that includes at least one raised or depressedregion, and the one or more layers of fibrous material include aplurality of discontinuous structural fibers and a thermoplasticmaterial connecting adjacent ones of the plurality of discontinuousstructural fibers. The disclosed composite article further includes athermoset matrix material. The thermoset matrix material is infusedwithin the one or more layers of fibrous material.

Other embodiments of the disclosed method for manufacturing a preform,the disclosed preform, and the disclosed composite article will becomeapparent from the following detailed description, the accompanyingdrawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram depicting one embodiment of a method formanufacturing a preform;

FIG. 2 is a flow diagram depicting one embodiment of a method formanufacturing a composite article;

FIG. 3 is a perspective view representing one or more layers of fibrousmaterial that include a first layer of fibrous material containing aplurality of discontinuous structural fibers, a second layer of fibrousmaterial containing a plurality of discontinuous structural fibers, anda third layer of thermoplastic material provided between the first andsecond layers of fibrous material;

FIG. 4 is a perspective view representing a thermoplastic material beinginfused into or coated onto one or more layers of fibrous material;

FIG. 5 is a perspective view of a composite article having a pluralityof ribs;

FIG. 6 is a perspective view of a composite article having a pluralityof beads;

FIG. 7 is view of robotic end effectors holding one or more layers offibrous material;

FIG. 8 is a view of the robotic end effectors of FIG. 7, in which therobotic end effectors press one or more layers of fibrous materialagainst a surface of an open mold;

FIG. 9 is view of a closed mold having one or more layers of fibrousmaterial between two opposing tool surfaces;

FIG. 10 is view of a tool surface having an overall shape having auniform cross-section;

FIG. 11 is a view of a tool surface having an overall shape having anon-uniform cross-section;

FIG. 12 is a flow diagram of an aircraft manufacturing and servicemethodology; and

FIG. 13 is a block diagram of an aircraft.

DETAILED DESCRIPTION

As illustrated in FIG. 1, a method for manufacturing a preform 100includes at Block 102 heating one or more layers of fibrous materialcontaining a plurality of discontinuous structural fibers and apredetermined percentage of thermoplastic material to a firsttemperature above a softening temperature of the thermoplastic material,at Block 104 forming the one or more layers of fibrous materialcontaining the thermoplastic material into a predetermined shapeincluding at least one raised or depressed region, and at Block 106cooling the one or more layers of fibrous material having thepredetermined shape to a second temperature below the softeningtemperature to harden the thermoplastic material. The predeterminedshape of the one or more layers of fibrous material is retained by thehardened thermoplastic material, and the cooled one or more layers offibrous material containing the thermoplastic material are permeable.

The preform may be an intermediate product used for manufacturing acomposite article. As illustrated in FIG. 2, a method for manufacturinga composite article 200 includes at Block 202 heating one or more layersof fibrous material containing a plurality of discontinuous structuralfibers and a predetermined percentage of thermoplastic material to afirst temperature above a softening temperature of the thermoplasticmaterial, at Block 204 forming the one or more layers of fibrousmaterial containing the thermoplastic material into a predeterminedshape including at least one raised or depressed region, at Block 206cooling the one or more layers of fibrous material having thepredetermined shape to a second temperature below the softeningtemperature to harden the thermoplastic material, wherein predeterminedshape of the one or more layers of fibrous material is retained by thehardened thermoplastic material, and wherein the cooled one or morelayers of fibrous material containing the thermoplastic material arepermeable, at Block 208 infusing the one or more layers of fibrousmaterial with a thermoset material, and at Block 210, curing thethermoset material.

The discontinuous structural fibers may provide for a main source ofstrength and stiffness to a composite article by carrying loads acrosstheir longitudinal directions. The material from which the discontinuousstructural fibers may be formed may include carbon, metals, alloys,glasses, ceramics, polymers, minerals, and combinations thereof. Forexample, the material from which the structural fibers are formed mayinclude aramids, polyolefins, carbon-based fibers, and boron-basedfibers. The material from which the thermoplastic fibers are formed mayinclude any of the following materials: polyamide, polyimide,polyamide-imide, polyester, polybutadiene, polyurethane, polypropylene,polyetherimide, polysulfone, polyethersulfone, polyphenylsulfone,polyphenylene sulfide, polyetherketone, polyetheretherketone,polyarylamide, polyketone, polyphthalamide, polyphenylene ether,polybutylene terephthalate, polyethylene terephthalate,polyester-polyarylate, polyaramid, polybenzoxazole, and viscose. Thethermoplastic fibers have a softening or melt temperature sufficientlylower than that of the structural fibers that the structural fibersremain essentially unchanged during the heating and softening/melting ofthe thermoplastic fibers. Otherwise, the structural fibers would softenand/or melt, and the beneficial effect of including the structuralfibers would be eliminated.

The plurality of discontinuous structural fibers may includediscontinuous structural fibers that are commonly oriented withneighboring discontinuous structural fibers. Commonly orienteddiscontinuous structural fibers may provide composite articles withdirectional mechanical properties. Various configurations of thecommonly oriented discontinuous structural fibers within the one or morelayers of fibrous material may be used. For example, a layer of fibrousmaterial may include a first plurality of discontinuous structuralfibers commonly oriented in a first direction and a second plurality ofdiscontinuous structural fibers commonly oriented in a second directiondifferent from the first direction. In another example, a first layer offibrous material may include discontinuous structural fibers that arecommonly oriented in a first direction, and a second layer of fibrousmaterial may include discontinuous structural fibers that are commonlyoriented in a second direction different from the first direction. Inyet another example, a first layer of fibrous material may include aplurality of discontinuous structural fibers commonly oriented in afirst direction, and a second layer of fibrous materials may includediscontinuous structural fibers that are randomly oriented. In yetanother example, a first layer of fibrous material and a second layer offibrous material may include discontinuous structural fibers that arecommonly oriented in the same direction.

The discontinuous structural fibers may have a length short enough thatthey may shift in their longitudinal directions with respect toneighboring discontinuous structural fibers during a forming step. Thediscontinuous structural fibers may have a length that depends on anumber of factors, such as the material from which the discontinuousstructural fibers are formed, other dimensions (e.g. width, diameter,and aspect ratio) of the discontinuous structural fibers, and thearrangement of discontinuous structural fibers within the one or morelayers of fibrous material. In an embodiment, the discontinuousstructural fibers may have a length short enough to permit thediscontinuous structural fibers to shift longitudinally with respect toneighboring discontinuous structural fibers during a forming step. Inanother embodiment, the discontinuous structural fibers may have alength of 8 in. or less, preferably a length of 6 in. or less, morepreferably a length of 4 in. or less.

As a length of the discontinuous structural fibers decreases, thediscontinuous structural fibers may more easily flow and conform tocomplex shapes. However, when discontinuous structural fibers are tooshort, achievable mechanical properties of the composite article maybecome limited. For example, short, discontinuous structural fibers maybe difficult to orient in a common direction, or short discontinuousstructural fibers may not maintain their common orientation during aforming step. In an embodiment, the discontinuous structural fibers mayhave a length long enough that they may be commonly oriented and maymaintain their common orientation with respect to neighboring structuralfibers during a forming step. The length may depend on a number offactors, such as a material from which the discontinuous structuralfibers are formed, other dimensions (e.g. width, diameter and aspectratio) of the discontinuous structural fibers, and an arrangement ofdiscontinuous structural fibers within the one or more layers of fibrousmaterial. In another embodiment, the discontinuous structural fibers mayhave a length of ¼ in. or greater, preferably a length of 1 in. orgreater, more preferably a length of 2 in. or greater.

In an embodiment, the discontinuous structural fibers may have a lengthin a range from ¼ in. to 8 in. preferably from 1 in. to 6 in., morepreferably from 2 in. to 4 in.

The discontinuous structural fibers may be made by any suitable method,such as cutting, chopping, or stretch-breaking.

An amount of the above-identified discontinuous structural fibers in thetotal amount of structural fibers is not limited and may be determinedby the desired properties of the composite article. However, if anamount of the above-identified discontinuous structural fibers in thetotal amount of structural fibers is too low, then the desired effectwill be limited. According to an embodiment, a layer of fibrous materialmay have discontinuous structural fibers included in a volume fractionof 50% or more with respect to a total volume of structural fibers inthe layer of fibrous material, more preferably a volume fraction of 60%or more, more preferably a volume fraction of 70% or more, morepreferably a volume fraction of 80% or more, more preferably a volumefraction of 90% or more, and more preferably a volume fraction of 100%.

The one or more layers of fibrous material contain a predeterminedpercentage of thermoplastic material. A thermoplastic material is amaterial that repeatedly changes from a hard solid state to a soft state(e.g. soft solid state or viscous liquid state) upon heating andreturning to the hard solid state upon cooling. The thermoplasticmaterial functions by becoming softened when the one or more layers offibrous material are heated to above a softening temperature of thethermoplastic material, thereby potentially facilitating a forming ofthe one or more layers of fibrous material, and by becoming hardenedwhen cooled to below the softening temperature, thereby retaining ashape provided to the one or more layers of fibrous material during theforming step.

If too little thermoplastic material is included in the one or morelayers of fibrous material, then a predetermined shape provided to theone or more layers of fibrous material during a forming step may not beretained upon cooling of the thermoplastic material. The amount ofthermoplastic material necessary to retain the predetermined shape maydepend on a number of factors, such as the material from which thethermoplastic material is formed, the dimensions and arrangement of thestructural fibers, and the severity of the geometry of the predeterminedshape to be retained. The predetermined shape to be retained by thethermoplastic material may be a near-net shape, not necessarily finisheddimensions, of a final component. In an embodiment, the amount ofthermoplastic material included in the one or more layers of fibrousmaterial may be determined to have a minimum amount sufficient to retaina shape provided to the one or more layers of fibrous material during aforming step. In another embodiment, the thermoplastic material may beincluded in a volume fraction of 0.1% or greater with respect to a totalvolume of the one or more layers of fibrous material, preferably avolume fraction of 1% or greater, more preferably a volume fraction of2% or greater.

If too much thermoplastic material is included in the one or more layersof fibrous material, then permeability will not be retained in the oneor more layers of fibrous material after forming and cooling, and thenthe resulting preform cannot be infused with a thermoset material. Theamount of thermoplastic material may depend on a number of factors, suchas the material from which the thermoplastic material is formed, thedimensions and arrangement of the structural fibers, and the amount ofthermoset material desired to be infused. In an embodiment, the amountof thermoplastic material included in the one or more layers of fibrousmaterial may be determined to have a maximum amount low enough to retaina permeability of the one or more layers of fibrous material. In anotherembodiment, the thermoplastic material may be included in a volumefraction of 20% or less with respect to a total volume of the one ormore layers of fibrous material, preferably a volume fraction of 10% orless, more preferably a volume fraction of 4% or less.

In an embodiment, the amount of thermoplastic material may be includedin a volume fraction of between 0.1% and 20% with respect to a totalvolume of the one or more layers of fibrous material, preferably between1% and 10%, more preferably between 2% and 4%.

The material from which the thermoplastic material is formed mayinclude, for example, a thermoplastic resin. The composition of thethermoplastic resin may be provided in any one of a variety ofcompositions. For example, the thermoplastic resin may include:acrylics, fluorocarbons, polyamides, polyethylenes, polyesters,polypropylenes, polycarbonates, polyurethanes, polyetheretherketones,polyetherketoneketones, polyetherimides, and combinations thereof.

The thermoplastic material may be provided to the one or more layers offibrous material in any manner. In an embodiment, one or more layers offibrous material may be made from a plurality of discontinuousstructural fibers and the thermoplastic material may be thereaftercombined with the one or more layers of fibrous material. For example,as represented by FIG. 3, one or more layers of fibrous material 300 mayinclude a first layer of fibrous material 302 containing a plurality ofdiscontinuous structural fibers, a second layer 304 of fibrous materialcontaining a plurality of discontinuous structural fibers, and a thirdlayer of thermoplastic material 306 may be provided between the firstand second layers of fibrous material. In another example, asrepresented by FIG. 4, a thermoplastic material 410 may be infused intoor coated onto one or more layers of fibrous material 400.

In another embodiment, a thermoplastic material may be combined with aplurality of discontinuous structural fibers and then the one or morelayers of fibrous material may be made therefrom. For example, athermoplastic material may be infused into or coated onto the pluralityof discontinuous structural fibers, and the one or more layers offibrous material may be made from the discontinuous structural fibershaving the thermoplastic material (not shown). Alternatively, the one ormore layers of fibrous material may be made from a plurality ofdiscontinuous structural fibers and a plurality of thermoplastic fibers(not shown).

The one or more layers of fibrous material may take a variety of formsand may include any assembly of structural fibers and thermoplasticmaterial. In an embodiment, the one or more layers of fibrous materialinclude a fabric. A layer of fabric may include a plurality ofdiscontinuous structural fibers interlaced to form a planar layer. Thestructural fibers may be interlaced in any manner to form the fabric.The fabric may include, for example, woven or non-woven fabric,multi-axial fabric, braided fabric, warp-knit fabric, or any one of avariety of other configurations of interlaced structural fibers.

A thermoplastic material may be provided with the one or more layers offabric in any manner. For example, a layer of thermoplastic material maybe combined with one or more layers of fabric. Alternatively, athermoplastic material may be infused into or coated onto one or morelayers of fabric, such as by spraying, brushing or rolling.

In another alternative, one or more layers of fabric may be formed byassembling a plurality of structural fibers with a thermoplasticmaterial. For example, a plurality of thermoplastic coated structuralfibers could be assembled to form a layer of fabric, or structuralfibers and thermoplastic fibers could be assembled to form a layer offabric.

In an embodiment, the one or more layers of fabric may be formed from ayarn. The yarn may include a plurality of the discontinuous structuralfibers aligned along a longitudinal direction of the yarn. Thediscontinuous structural fibers may be staple fibers such that they areoverlapped and staggered with respect to neighboring structural fibersto provide a length of yarn that is greater than the length of anyconstituent structural fiber. A thermoplastic material may be providedwith the yarn to form one or more layers of fabric in any manner. Forexample, one or more layers of fabric may be formed from the yarn and alayer of thermoplastic material may be included with or between the oneor more layers of the fabric. In another example, a thermoplasticmaterial may be infused into or coated onto one or more layers of fabricafter the one or more layers of fabric are formed from the yarn.

In yet another example, the yarn may include a thermoplastic materialwith the plurality of the discontinuous structural fibers, and the oneor more layers of fabric may be formed from the yarn having thethermoplastic material. The thermoplastic material may be included inthe yarn in any manner. For example, a thermoplastic material may beadded to the yarn after the yard is formed, such as by infusingthermoplastic material into or coating thermoplastic material onto theyarn after the yarn is formed. In another example, a yarn may be formedby assembling a plurality of discontinuous structural fibers with athermoplastic material. In this case, a plurality ofthermoplastic-coated discontinuous structural fibers could be assembledto form a length of yarn, or a plurality of discontinuous structuralfibers and one or more thermoplastic fibers could be assembled to form alength of yarn.

In yet another example, the yarn may include a thermoplastic materialwith the plurality of the discontinuous structural fibers in an intimateblend. An intimate-blend yarn refers to yarn created from two or morestaple (i.e. discontinuous) fibers in a spun yarn that has been blendedso that the individual fibers do not retain their individualcharacteristics. In this case, each length of yarn comprises apercentage of structural and thermoplastic fibers that are randomlydistributed both through the cross section and along the length of theyarn.

The thermoplastic material included with the yarn may aid to holdtogether the discontinuous structural fibers together in the yarn.

The method further includes heating the one or more layers of fibrousmaterial to a first temperature above a softening temperature of thethermoplastic material. The heating functions to soften thethermoplastic material, which may become pliable or flow when the one ormore layers of fibrous material are heated to above a softeningtemperature of the thermoplastic material, and thereby may facilitate aforming of the one or more layers of fibrous material.

The softening temperature depends on the material from which thethermoplastic material is formed. The softening temperature is thetemperature at which the thermoplastic material repeatedly becomessoftened when heated and hardened when cooled, thereby facilitating aforming of the one or more layers of fibrous material when thethermoplastic material is heated to become soft, and retaining a shapeprovided to the one or more layers of fibrous material when thethermoplastic material is cooled to become hard. The thermoplasticmaterial is selected to have a softening temperature below a meltingtemperature of the structural fibers.

The method of heating may include any manner of heating the one or morelayers of fibrous material. For example, the heating may includeconductive heating, radiation heating, or inductive heating. However, aheating device may be provided in a variety of configurations and is notlimited to heating using conductive heating, radiation heating, orinductive heating. A heating device for implementing the heating stepmay be provided as a separate component or together with one or moreother components. In an example, the one or more layers of fibrousmaterial may be heated in a conveyor oven to soften the thermoplasticmaterial. In another example, the one or more layers of fibrous materialmay be heated by a mold used for a forming step, either before, during,or after a forming step.

The method further includes forming the one or more layers of fibrousmaterial containing the thermoplastic material into a predeterminedshape including at least one raised or depressed region. The forming mayinclude any process for providing a shape including at least one raisedor depressed region to the one or more layers of fibrous material. Themethod may include a single forming step or a plurality of formingsteps.

The predetermined shape provided by the forming step may include anoverall shape of a resulting composite article. The overall shapeprovided to the one or more layers of fibrous material is not limited.For example, the overall shape may have a uniform cross-section ornon-uniform cross section. The predetermined shape provided by theforming step may include one or more localized raised or depressedregions. The localized regions may include a variety of structuralformations to enhance the strength and/or rigidity of a resultingcomposite article with respect to a particular direction. For example,the predetermined shape may include one or more ribs 502 that extendinglinearly across at least a portion of a composite article 500 as shownin FIG. 5, or the predetermined shape may include a plurality of beads602 across an area of at least a portion of a composite article 600 asshown in FIG. 6. The plurality of beads may extend in a repeating ornon-repeating pattern across an area of at least a portion of thecomposite article.

The forming of the one or more layers of fibrous material may includeforming while the thermoplastic material is in a softened state.Although the scope is not limited by theory, it is believed that formingthe one or more layers of fibrous material while the thermoplasticmaterial is in a softened state may facilitate longitudinal displacementof neighboring discontinuous structural fibers, thereby permitting theone or more layers of fibrous material to more readily conform tocomplex shapes without wrinkling. However, the method is not necessarilylimited to forming while the thermoplastic material is in a softenedstate. For example, a thermoplastic could be incorporated into the oneor more layers of fibrous material in a manner that would not restrictlongitudinal displacement of the structural fibers, and the heating stepcould be performed during or after the forming of the one or more layersof fibrous material, such that the thermoplastic material flows withinthe one or more layers of fibrous material when heated and hardens uponcooling to retain the predetermined shaped provided to the one or morelayers of fibrous material.

In the case of forming multiple layers of fibrous material, the multiplelayers of fibrous material may be shaped together as a unit or inseparate groups, e.g. one at a time, two at a time, etc.

In an embodiment, the forming may include the use of at least one mold.For example, the forming may include at least one of an open mold and aclosed mold process.

An open-mold process may include providing the one or more layers offibrous material onto a first surface of a tool and pressing the one ormore layers to a first shape of the first surface of the tool, such asby pressing selected regions or the entireties of the one or more layersto the first shape of the first surface of the tool. The pressing mayprovide the one or more layers of fibrous material with an overall shapeof a composite article. For example, a first surface 1000 of a tool mayinclude an overall shape having a uniform cross section as shown in FIG.10 or a first surface 1100 of a tool may include an overall shape havinga non-uniform cross section as shown in FIG. 11. The pressing may beperformed manually or automatically.

In one embodiment of an open-mold process, as illustrated in FIGS. 7 and8, robotic end effectors 702 may be used to press one or more layers offibrous material 704 against a first surface of a tool of an open mold706 having the predetermined shape including at least one raised ordepressed region 708. The use of robotic end effectors 702 to pressagainst the first surface of the tool of the open mold 706 may providereliability and repeatability for mass manufacturing of compositearticles.

As illustrated in FIG. 9, a closed-mold process may include providingthe one or more layers of fibrous material 902 between two opposing toolsurfaces, e.g. first surface 904 of a first tool having a first shapeand a second surface 906 of a second tool having a second shape, andpressing the opposing tool surfaces together. The pressing may providethe one or more layers of fibrous material with an overall shape of acomposite article. For example, a first surface 1000 of a first tool mayinclude an overall shape having a uniform cross section as shown in FIG.10 or a first surface 1100 of a first tool may include an overall shapehaving a non-uniform cross section as shown in FIG. 11. The pressing mayalso provide the one or more layers of fibrous material with one or morelocalized raised or depressed regions as described above.

In one embodiment, the method may include a first forming step and asecond forming step. The first forming step may provide the one or morelayers of fibrous material with an overall shape of a composite articleand a second forming step may provide the one or more layers of fibrousmaterial with a more precise form of the overall shape of the compositearticle and/or may provide the one or more layers of fibrous materialwith a shape of one or more localized raised or depressed regions asdescribed above.

For example, the first forming step may use an open mold, in which theone or more layers of fibrous material are provided onto a first surfaceof a first tool, the first surface having a first shape, and the one ormore layers of fibrous material are formed (e.g. pressed) to the firstshape of the first surface of the first tool using robotic endeffectors. The second forming step may be performed after the roboticend effectors are removed and a second mold is positioned to oppose thefirst mold. In the second forming step, the one or more layers offibrous material may be disposed between the first surface of the firsttool and a second surface of the second tool, the second surface havinga second shape, and the one or more layers of fibrous material may beformed (e.g. pressed) to the first shape of the first surface of firsttool and the second shape of the second surface of the second tool.Forming the one or more layers of fibrous material between the firstsurface and the second surface may provide the one or more layers offibrous material with a more precise overall shape of a compositearticle and/or one or more localized raised or depressed regions asdescribed above.

The method further includes cooling the one or more layers of fibrousmaterial having the predetermined shape to a second temperature belowthe softening temperature to harden the thermoplastic material, whereinthe predetermined shape of the one or more layers of fibrous material isretained by the hardened thermoplastic material, wherein the cooled oneor more layers of fibrous material containing the thermoplastic materialare permeable.

The cooling functions to harden the thermoplastic material. The coolingmay include any manner of cooling the one or more layers of fibrousmaterial. For example, the cooling may include permitting the one ormore layers of fibrous material to cooling at room temperature or mayinclude active refrigerating the one or more layers of fibrous material.

In an embodiment, a forming device used in a step of forming may includea cooling device for reducing a temperature of the thermoplasticmaterial in the one or more layers of fibrous material. The coolingdevice may be integrated into or mounted to a mold used for forming. Thecooling device may also be located downstream of the forming device.

The cooling device may draw heat away from the thermoplastic material toallow the thermoplastic material to cool and harden in a manner suchthat the shape provided during the forming is retained. In anembodiment, the cooling device reduces the temperature of thethermoplastic material below the softening temperature after the one ormore layers of fibrous material is formed. In another embodiment, theone or more layers of fibrous material may be formed as thethermoplastic material cools.

In an embodiment, the cooling device may include one or more conduitsfor circulating a cooling medium such as any suitable liquid (e.g.,water) through upper and/or lower forming molds. The cooling medium maydraw heat away from a portion of the upper and/or lower forming molds,which may allow the thermoplastic material to cool.

As previously described, the thermoplastic material is included anamount sufficient to retain a shape provided to the one or more layersof fibrous material during a forming step and an amount sufficient toretain a permeability of the one or more layers of fibrous materialafter forming.

After cooling, the resulting intermediate product may be referenced as a“preform”, which may be used for the manufacture of a composite article.The preform includes one or more layers of fibrous material. The one ormore layers of fibrous material are permeable and have a shape thatincludes at least one raised or depressed region. The one or more layersof fibrous material include a plurality of discontinuous structuralfibers and a thermoplastic material retaining the shape of the one ormore layers of fibrous material.

By retaining the predetermined shape provided during forming, thepreform may be formed to a near-net shape of a composite article that isretained during subsequent handling steps.

By retaining a permeability therein, the preform may be infused with athermoset matrix material during a method for manufacturing a compositearticle.

The thermoplastic material may be present in a volume fraction ofbetween 0.1% and 20% with respect to a total volume of the preform, morepreferably between 1% and 10% with respect to a total volume of thepreform, more preferably between 2% and 4% with respect to a totalvolume of the preform.

A method for manufacturing a composite article may use a preformmanufactured as described above. The method for manufacturing acomposite article further includes infusing the permeable preform with athermoset matrix material, and curing the thermoset matrix material.

The thermoset matrix material functions to hold the structural fiberstogether, to transfer stresses between neighboring structural fibers,and to protect the structural fibers from mechanical and/orenvironmental damages.

The thermoset matrix material can be infused into the permeable preformwhile in the soft solid state or viscous liquid state and can be curedto form a hardened matrix of the resulting composite article. Thethermoset matrix material may be selected to have a curing temperaturethat is below a softening temperature of the thermoplastic material.

The material from which the thermoset matrix material is formed mayinclude, for example, a thermoset resin. The composition of thethermoset resin may be provided in any one of a variety of compositions.For example, the thermoset resin may include, for example, epoxy, vinylester, bismaleimide, benzoxazine, polyimide, phthalonitrile, cyanateester, and combinations thereof.

Infusing may include any method for providing thermoset matrix materialinto the permeable preform.

Curing may include any method for application of heat and optionallypressure to cross-link and harden the thermoset matrix material.

The composite article includes one or more layers of fibrous materialand a thermoset matrix material. The one or more layers of fibrousmaterial have a shape that includes at least one raised or depressedregion. The one or more layers of fibrous material include a pluralityof discontinuous structural fibers and a thermoplastic materialconnecting adjacent ones of the plurality of discontinuous structuralfibers. The thermoset matrix material is infused within the one or morelayers of fibrous material.

The composite article may be, for example, a component of an aircraft ora spacecraft.

In an embodiment, the discontinuous structural fibers are present in avolume fraction of between 30% to 70% with respect to a total volume ofthe composite article, preferably between 40% and 60% with respect to atotal volume of the composite article.

In an embodiment, the thermoset matrix material is present in a volumefraction of between 30% to 70% with respect to a total volume of thecomposite article, preferably between 40% and 60% with respect to atotal volume of the composite article.

It will be understood by persons skilled in the art that the method mayinclude various other steps, modifications, and alternatives, such asfollows.

It will be understood that the one or more layers of fibrous materialmay include additional filler or modifiers.

It will be understood that the method for manufacturing a preform mayinclude one or more additional steps.

The method may include a step of transporting the one or more layers offibrous material from a heating device to a forming device, such byusing robotic end effectors, which may be the same or different fromrobotic end effectors used in forming the one or more layers of fibrousmaterial.

The method may include a step of assembling and/or cutting the one ormore layers of fibrous material before forming.

The method may include one or more additional layers of fibrous materialadded before forming. For example, the one or more additional layers offibrous material may contain continuous structural fibers rather thandiscontinuous structural fibers. In an example, a first layer of fibrousmaterial may be made from discontinuous structural fibers and a secondlayer of fibrous material may be made from continuous structural fibers.In this case, the second layer of fibrous material may be provided toregions of the preform where conforming to complex shapes is notrequired. Continuous structural fibers may beneficially provide acomposite article with strength and stiffness in the orientationdirection of the structural fibers, but continuous structural fibers maynot sufficiently shift in their longitudinal directions during a formingstep and, thereby, may causing wrinkling when forming to complex shapes.Accordingly, discontinuous structural fibers may be used in regionswhere conforming to complex shapes is required.

It will be understood that the method may include cutting the resultingpreform after forming, handling and transporting the preform afterforming, or positioning the preform with other preforms or withadditional layers of fibrous material.

Examples of the present disclosure may be described in the context of anaircraft manufacturing and service method 1200 as shown in FIG. 12 andan aircraft 1300 as shown in FIG. 13. During pre-production, theillustrative method 1200 may include specification and design, as shownat Block 1202, of the aircraft 1300 and material procurement, as shownat Block 1204. During production, component and subassemblymanufacturing, as shown at Block 1206, and system integration, as shownat Block 1208, of the aircraft 1300 may take place. Thereafter, theaircraft 1300 may go through certification and delivery, as shown Block1210, to be placed in service, as shown at Block 1212. While in service,the aircraft 1300 may be scheduled for routine maintenance and service,as shown at Block 1214. Routine maintenance and service may includemodification, reconfiguration, refurbishment, etc., of one or moresystems of the aircraft 1300.

Each of the processes of illustrative method 1200 may be performed orcarried out by a system integrator, a third party, and/or an operator(e.g., a customer). For the purposes of this description, a systemintegrator may include, without limitation, any number of aircraftmanufacturers and major-system subcontractors; a third party mayinclude, without limitation, any number of vendors, subcontractors, andsuppliers; and an operator may be an airline, leasing company, militaryentity, service organization, and so on.

As shown in FIG. 13, the aircraft 1300 produced by illustrative method1200 (FIG. 12) may include airframe 1302 with a plurality of high-levelsystems 1304 and interior 1306. Examples of high-level systems 1304 mayinclude one or more of propulsion system 1308, electrical system 1310,hydraulic system 1312, and environmental system 1314. Any number ofother systems may be included. Although an aerospace example is shown,the principles disclosed herein may be applied to other industries, suchas the automotive and marine industries. Accordingly, in addition to theaircraft 1300, the principles disclosed herein may apply to othervehicles (e.g., land vehicles, marine vehicles, space vehicles, etc.).

The disclosed method for manufacturing a preform, the disclosed preform,and the disclosed composite article may be employed during any one ormore of the stages of the manufacturing and service method 1200. Forexample, the aircraft 1300 may be reconfigured or refurbished duringroutine maintenance and service (Block 1214) to include the compositearticle. Also, the disclosed method for manufacturing a preform, thedisclosed preform, and the disclosed composite article may be utilizedduring production stages (Blocks 1206 and 1208). Similarly, thedisclosed method for manufacturing a preform, the disclosed preform, andthe disclosed composite article may be utilized, for example and withoutlimitation, while aircraft 1300 is in service (Block 1212) and/or duringthe maintenance and service stage (Block 1214).

Although various embodiments of the disclosed method for manufacturing apreform, the disclosed preform, and the disclosed composite article havebeen shown and described, modifications may occur to those skilled inthe art upon reading the specification. The present application includessuch modifications and is limited only by the scope of the claims. Otherembodiments of the will become apparent from the following detaileddescription, the accompanying drawings and the appended claims.

What is claimed is:
 1. A method for manufacturing a preform comprising:heating one or more layers of fibrous material containing a plurality ofdiscontinuous structural fibers and a predetermined percentage ofthermoplastic material to a first temperature above a softeningtemperature of said thermoplastic material; forming said one or morelayers of fibrous material containing said thermoplastic material into apredetermined shape including at least one raised or depressed region;and cooling said one or more layers of fibrous material having thepredetermined shape to a second temperature below said softeningtemperature to harden said thermoplastic material, wherein saidpredetermined shape of said one or more layers of fibrous material isretained by said hardened thermoplastic material, and wherein saidcooled one or more layers of fibrous material containing saidthermoplastic material are permeable.
 2. The method of claim 1 whereinsaid one or more layers of fibrous material includes one or more layersof fabric.
 3. The method of claim 2 wherein at least one layer of fabricincludes yarn, wherein said yarn includes a plurality of discontinuousstructural fibers aligned along a longitudinal direction of the yarn anda predetermined percentage of thermoplastic material.
 4. The method ofclaim 1 wherein overlapped ones of said plurality of discontinuousstructural fibers move longitudinally relative to each other during saidforming of said one or more layers of fibrous material into saidpredetermined shape.
 5. The method of claim 1 wherein said predeterminedpercentage of thermoplastic material retains said predetermined shapeprovided to said one or more layers of fibrous material upon saidcooling of said one or more layers of fibrous material.
 6. The method ofclaim 1 wherein said predetermined percentage of thermoplastic materialretains a permeability of said one or more layers of fibrous materialupon said cooling.
 7. The method of claim 1 wherein said predeterminedpercentage of thermoplastic material is a volume fraction of between0.1% and 20% with respect to a total volume of said one or more layersof fibrous material.
 8. The method of claim 1 wherein said predeterminedpercentage of thermoplastic material is a volume fraction of between 1%and 10% with respect to a total volume of said one or more layers offibrous material.
 9. The method of claim 1 wherein said forming the oneor more layers of fibrous material into a predetermined shape includes:providing said one or more layers of fibrous material onto a firstsurface of a first tool, said first surface having a first shape; andforming said one or more layers of fibrous material to said first shapeof said first surface of said first tool.
 10. The method of claim 9wherein said forming said one or more layers of fibrous material to saidshape of said first surface of said first tool is by way of usingrobotic end effectors.
 11. The method of claim 1 wherein said formingsaid one or more layers of fibrous material into a predetermined shapeincludes providing said one or more layers of fibrous material between afirst surface of a first tool, said first surface having a first shape,and a second surface of a second tool, said second surface having asecond shape, and forming said one or more layers of fibrous material tothe shapes of said first and second shapes of said first and secondsurfaces of said first and second tools.
 12. The method of claim 1wherein said forming said one or more layers of fibrous material into apredetermined shape includes: providing said one or more layers offibrous material onto a first surface of a first tool, said firstsurface having a first shape; forming said one or more layers of fibrousmaterial to said first shape of said first surface of said first toolusing robotic end effectors; removing said robotic end effectors;positioning a second tool to oppose said first tool, said one or morelayers of fibrous material disposed between said first surface of saidfirst tool and a second surface of said second tool, said second surfacehaving a second shape; and forming said one or more layers of fibrousmaterial to said first shape of said first surface of said first tooland said second shape of said second surface of said second tool.
 13. Apreform comprising: one or more layers of fibrous material, wherein saidone or more layers of fibrous material are permeable and have a shapethat includes at least one raised or depressed region, wherein said oneor more layers of fibrous material comprise: a plurality ofdiscontinuous structural fibers; and a thermoplastic material retainingsaid shape of said one or more layers of fibrous material.
 14. Thepreform of claim 13 wherein said one or more layers of fibrous materialincludes one or more layers of fabric.
 15. The preform of claim 14wherein at least one layer of fabric includes yarn, wherein said yarnincludes a plurality of discontinuous structural fibers aligned along alongitudinal direction of said yarn and a predetermined percentage ofthermoplastic material.
 16. The preform of claim 13 wherein saidpredetermined percentage of thermoplastic material is a volume fractionof between 0.1% and 20% with respect to a total volume of said one ormore layers of fibrous material.
 17. The preform of claim 13 whereinsaid predetermined percentage of thermoplastic material is a volumefraction of between 1% and 10% with respect to a total volume of saidone or more layers of fibrous material.
 18. A composite articlecomprising: one or more layers of fibrous material, wherein said one ormore layers of fibrous material have a shape that includes at least oneraised or depressed region, wherein said one or more layers of fibrousmaterial comprise: a plurality of discontinuous structural fibers; and athermoplastic material connecting adjacent ones of said plurality ofdiscontinuous structural fibers; and a thermoset matrix material infusedwithin said one or more layers of fibrous material.
 19. The compositearticle of claim 18 wherein said discontinuous structural fibers arepresent in a volume fraction of between 30% to 70% with respect to atotal volume of the composite article.
 20. The composite article ofclaim 18 wherein said thermoset matrix material is present in a volumefraction of between 30% to 70% with respect to a total volume of thecomposite article. method for manufacturing a preform comprising:heating one or more layers of fibrous material containing a plurality ofdiscontinuous structural fibers and a predetermined percentage ofthermoplastic material to a first temperature above a softeningtemperature of said thermoplastic material; forming said one or morelayers of fibrous material containing said thermoplastic material into apredetermined shape including at least one raised or depressed region;and cooling said one or more layers of fibrous material having thepredetermined shape to a second temperature below said softeningtemperature to harden said thermoplastic material, wherein saidpredetermined shape of said one or more layers of fibrous material isretained by said hardened thermoplastic material, and wherein saidcooled one or more layers of fibrous material containing saidthermoplastic material are permeable.